An illumination apparatus includes a housing, a light source, a centrifugal fan, and a heat sink. The housing has an accommodation, a plurality of inlets, and a plurality of outlets. The accommodation communicates with the outside of the housing through the inlets and the outlets. The light source, the centrifugal fan, and the heat sink are disposed in the accommodation. The heat sink includes a base and a plurality of fins connected to the base. The base is connected to the light source, the fins radially surround the centrifugal fan. An air channel is disposed between two adjacent fins. An air from the outside of the housing is capable of flowing into the accommodation through the inlets and then into the centrifugal fan in an axial direction of the centrifugal fan, and flow out of the accommodation in a radial direction of the centrifugal fan through the air channel and outlets.